"Metallic glass" is an amorphous ferromagnetic material. Such material can be used in the construction of electrical equipment to reduce core losses. The problems associated with forming bulk objects from thin metallic glass ribbons (sometimes referred to as amorphous ribbons) are described in U.S. Pat. No. 4,529,458 which teaches stacking the ribbon and consolidating the alloy under a pressure of at least 5895 kPa at a temperature of between 70% and 90% of the crystallisation temperature of the ribbon material for a time sufficient to facilitate bonding of the ribbons into a bulk object.
U.S. Pat. No. 4,529,458 also discloses other methods of forming bulk objects such as the method revealed in U.S. Pat. No. 4,298,382 involving hot pressing finely dimensioned bodies with forces of at least 6895 kPa in a non-oxidising environment at temperatures ranging from about 25.degree. C. below the glass transition temperature to about 15% above the glass transition temperature for a period of time sufficient to cause the bodies to flow and fuse together into an integral unit.
The methods described have the following common steps:
Preheating the ribbons; bringing the ribbons into contact; compacting the block of ribbons and heat treating the bulk object to be formed.
Preheating the ribbons makes them brittle and very prone to damage, consequently material losses and production delays are common.
Even the finished bulk product of the process described above is relatively brittle, consequently breakages and imperfections are common.
Metallic glass blocks and ribbons are so hard that their shape cannot be easily or reliably changed by conventional cutting methods, even though a ribbon is flexible. Guillotine or blank die cutting methods stress and crack the blocks, laser and EDM cutting methods melt the metallic glass and create undesirable crystallisation which reduces the ferromagnetic properties of the material. Furthermore, some of these cutting methods create undesirable magnetic and electrical connections between laminated ribbons in the block which propagate undesirable eddy currents. Thus these cutting methods further reduce the ferromagnetic properties of laminated metallic glass blocks.
In some applications, the individual ribbon portions are heated to pre-anneal the material so that it will have good ferromagnetic properties when one or more strategically located strips of material are required in an electrical device. However, pre-annealing makes the ribbons very brittle.
The use of metallic glass (amorphous magnetic) ribbons annealed or un-annealed on stators and other parts of electric motors, either singly or in laminations, is common. For example, rotary electric machines like those described in Canadian Patent No 1136199 are made by adhering amorphous magnetic material ribbons to the stator core coil. Alternatively, a magnetic wedge can be fitted into the stator slot of the motor where the magnetic wedge consists of an amorphous magnetic ribbon adhered onto a non-magnetic, insulating sheet of the type described in U.S. Pat. No. 5,252,877.
However the methods described above for producing cores for rotors and stators is time consuming. Furthermore, the brittleness of the typically pre-annealed amorphous magnetic material results in high production losses.
Other ways of producing parts of electric and even servo-electric motors include winding wire shaped amorphous magnetic material around a cylindrical coil or producing a stator from one or two edge wound helices of amorphous magnetic ribbon as described in U.S. Pat. No. 4,392,073. These types of construction are not common because of high manufacturing costs.
Certain solid forms of motor cores can be moulded by mixing amorphous magnetic material in the form of flakes and short fibres with a thermosetting polymer binder. It is, however, recognised that the packing density of the amorphous material is not always consistent and sufficiently dense for desirable results.
To provide some of the conventional shapes of transformer coils and the like, stacks of ribbons are arranged into the desired shapes, however it is found that the final product does not perform as well as would a substantially solid or shaped metallic glass block cut to the conventional shape.
For example, the E.vertline. shaped core of a three phase transformer winding can be constructed using stacks of metallic glass ribbons. The E.vertline. shaped core is created by nesting and stacking rectangular blocks of laminated and treated ribbons in the shape depicted in FIG. 15. However, gaps still exist between the ends of the rectangular blocks and these gaps contribute to a decrease in the ferromagnetic characteristics of the object compared with a solid core of the same material which obviously does not have the gaps.
The advantages of substantially solid laminated amorphous magnetic material which has been annealed over conventional permanent magnet or iron core material include; reduced core loss; high permeability; high moments of inertia; high heat dissipation; less radio frequency emission in high speed motors that can be made without commutators and brushes; and in some motor designs substantially constant torque across the voltage and revolutions per minute range.
Therefore, it is desirable to have the advantages described and to overcome or avoid the abovementioned problems.
A method for manufacturing and annealing bulk metallic glass objects for use in electrical products such as those described above is described in this specification as well as a variety of electric motor components which become possible as a consequence of the use of the method.